Clean up loading code

- Centralized instantiation of the PEFT wrapper in `make_policy` for inference
  (e.g. in `lerobot-record`)
- Training a PEFT policy also sets `cfg.use_peft` so that all inference code loading
  the policy can rely on that attribute to identify if PEFT loading is needed
- Modified RTC example to also include PEFT policies. Mostly because this is an example
  I'm currently exploring.

src/lerobot/scripts/lerobot_record.py

@@ -194,15 +194,9 @@ class RecordConfig:
         if policy_path:
             cli_overrides = parser.get_cli_overrides("policy")
 
-            # In case of a PEFT model We assume that the user saved the policy config (`config.json`) alongside the
-            # adapter parameters / config. If they didn't we could instantiate the default configuration for the policy
-            # but we wouldn't know if that is correct. So, in case of a missing config this will simply fail.
             self.policy = PreTrainedConfig.from_pretrained(policy_path, cli_overrides=cli_overrides)
             self.policy.pretrained_path = policy_path
 
-            if (Path(policy_path) / "adapter_config.json").exists():
-                self.policy.use_peft = True
-
         if self.teleop is None and self.policy is None:
             raise ValueError("Choose a policy, a teleoperator or both to control the robot")
 
@@ -433,19 +427,7 @@ def record(cfg: RecordConfig) -> LeRobotDataset:
         )
 
     # Load pretrained policy
-    if cfg.policy and cfg.policy.use_peft:
-        from peft import PeftModel
-
-        logging.info("Loading policy's PEFT adapter.")
-        # in case of PEFT we re-use the policy pretrained path to point to the adapter path.
-        peft_path = cfg.policy.pretrained_path
-        cfg.policy.pretrained_path = None
-
-        policy = make_policy(cfg.policy, ds_meta=dataset.meta)
-        policy = PeftModel.from_pretrained(policy, peft_path)
-
-    else:
-        policy = None if cfg.policy is None else make_policy(cfg.policy, ds_meta=dataset.meta)
+    policy = None if cfg.policy is None else make_policy(cfg.policy, ds_meta=dataset.meta)
 
     preprocessor = None
     postprocessor = None